1. Field of the Invention
The invention relates to flexible microsurgical instruments. More particularly, the invention relates to a sheath which covers the flexible coil of a flexible microsurgical instrument and which has a tactile and a visual position indicator.
2. State of the Art
Flexible microsurgical instruments, in particular endoscopic biopsy forceps, are used for taking tissue samples from the human body for analysis. These instruments typically have a long (e.g. 8 feet) flexible coil containing one or more control wires coupled to a proximal actuating handle. The actuating handle moves the control wires relative to the coil to effect a tissue sampling operation at the distal end of the coil. A pair of forceps jaws are mounted on a clevis at the distal end of the coil. The forceps jaws are coupled to the control wires so that movement of the control wires causes the jaws to open and close to bite a tissue sample.
The endoscopic biopsy procedure is accomplished through an endoscope which is inserted into a body and guided by manipulation to the biopsy site. The endoscope typically includes a long narrow flexible tube with an optical lens and a narrow lumen for receiving a biopsy forceps. The practitioner guides the endoscope to the biopsy site while looking through the optical lens and inserts the biopsy forceps through the lumen of the endoscope to the biopsy site. While viewing the biopsy site through the optical lens of the endoscope, the practitioner manipulates the actuating handle to effect a tissue sampling operation at the distal end of the instrument. After a sample has been obtained, the practitioner and/or an assistant carefully withdraws the instrument from the endoscope while holding the actuating handle to maintain the jaws in a closed position lest the sample be lost inside the endoscope. The flexible coil of the instrument is "springy" and subject to a whip-like behavior as the jaws of the instrument are withdrawn from the endoscope. If the coil is withdrawn from the endoscope too quickly, the jaws of the instrument will be whipped through the air as they exit the endoscope and result in the possible loss or contamination of the biopsy sample. Therefore, the practitioner and/or the assistant must be very careful in withdrawing the flexible coil of the instrument to be aware of when the jaws will exit the endoscope.